In recent years, in mobile communication using radio waves, various information other than voice data such as image data and moving image data etc. has become the target of communication. In accordance with this, high-speed and large capacity wireless data communication is also sought after. It is known that when high-speed transmission is carried out in mobile communication, the influence of wave delays due to multipath cannot be ignored, and the reception performance deterioration may caused due to frequency selective fading.
OFDM (Orthogonal Frequency Division Multiplexing) schemes have been a focus of attention as an example of frequency selective fading, and of these, various investigations have taken place into the MC (Multi Carrier)-CDMA schemes (also referred to as the “OFCDM scheme”) that is the combination with the CDMA (Code Division Multiple Access) scheme. MC-CDMA schemes are mainly classified into spreading in a time domain and spreading in a frequency domain (in the following, collectively referred to as “one-dimensional spreading”) (for example, refer to non-patent document 1). FIG. 1A shows typical mapping of spreaded symbol in a frequency domain, and FIG. 1B shows typical mapping of spreaded symbol in a time domain.
In a wireless transmission method using frequency domain spreading, a plurality of chips generated by spreading of the modulation symbols are arranged at different subcarriers at the same time. On the other hand, in a wireless transmission method using the time domain spreading, a plurality of chips generated by spreading of modulation symbols are arranged at different OFDM symbols at the same frequency.
Non-Patent Document: A study on time domain spreading for OFCDM, Technical Report of IEICE, RCS2001-179.